Question: 

what are the materials used for FDM and LOM process, their characteristics, mechanical properties and applications? Discuss them. 

Answer: 

Fused Deposition Modeling (FDM) and Laminated Object Manufacturing (LOM) use very different materials, each with distinct characteristics and applications. The choice of material directly impacts a part's mechanical properties and its suitability for a given task.

FDM Materials 

FDM uses a variety of thermoplastic filaments. These plastics are melted and extruded to form an object layer by layer. The most common materials are:

Characteristics and Mechanical Properties

• PLA (Polylactic Acid): This is the most popular FDM material, known for being easy to print.

  • Characteristics: It's a bio-sourced and biodegradable plastic, odorless, and comes in many colors. It has a glossy finish.

  • Mechanical Properties: It's quite rigid and has good tensile strength, but it's brittle and has a low maximum service temperature (~52°C), making it unsuitable for high-stress or high-heat applications.

• ABS (Acrylonitrile Butadiene Styrene): A common engineering thermoplastic.

  • Characteristics: Known for its toughness, durability, and heat resistance. It requires a heated print bed and can produce a strong odor during printing. It has a matte finish and can be post-processed with acetone to create a smooth, glossy surface.

  • Mechanical Properties: It has superior impact resistance and is more flexible than PLA, making it more durable for functional prototypes. Its glass transition temperature is higher (~105°C).

• PETG (Polyethylene Terephthalate Glycol): A blend of PET and glycol.

  • Characteristics: It's a balance between PLA and ABS, offering ease of use with higher strength, durability, and chemical resistance. It's often used for parts that need to be waterproof or food-safe.

  • Mechanical Properties: It's less brittle than PLA and more durable and flexible than ABS, with good layer adhesion.

• Nylon and Composites: Advanced FDM materials for specialized applications.

  • Characteristics: Nylon is very strong and wear-resistant. Composites (e.g., carbon fiber or fiberglass-infused filaments) are used to create extremely rigid and strong parts.

  • Mechanical Properties: They have excellent tensile and impact strength, making them suitable for high-performance applications.

Applications

FDM is widely used for rapid prototyping, functional prototypes, and creating custom jigs, fixtures, and tooling. Its materials are suitable for a range of uses from simple concept models (PLA) to end-use parts (ABS, Nylon, Composites) that require specific mechanical properties.

LOM Materials

LOM uses sheets of material that are layered, bonded, and cut to create a 3D object.

Characteristics and Mechanical Properties

• Paper: This is the most common and cost-effective LOM material.

  • Characteristics: It's readily available, inexpensive, and results in a final object with wood-like properties. It can also be post-processed with sanding and sealing to improve its finish and moisture resistance. Color LOM uses a colored paper feedstock, allowing for full-color models.

  • Mechanical Properties: The strength of laminated paper is surprisingly high due to the bonding process, but it's not suitable for high-stress structural applications. The strength is dependent on the adhesive and layer thickness.

• Plastic and Metal Foils: While less common, LOM can also use adhesive-coated plastic and metal sheets.

  • Characteristics: These materials offer more durability and different properties than paper. However, they are more difficult to cut and the process is less common for these materials compared to other technologies like SLA or SLS.

  • Mechanical Properties: The resulting parts are more robust than paper models, with properties that align with the parent material. For example, laminated metal foil can create patterns for metal casting.

Applications

LOM is best for low-cost, large-scale prototypes and models where aesthetic appearance is more important than fine detail or high mechanical strength.

• Architectural Models: Due to its ability to create large objects quickly and at a low cost, LOM is ideal for producing building and landscape models.

• Casting Patterns: The wood-like properties of laminated paper make it suitable for creating patterns for sand casting.

• Visual Prototypes: It's used to create large-scale visual models for presentation or conceptual design, especially when a realistic, solid feel is desired.